(1) Field of the Invention
The present invention relates to interfacing of a user terminal of an automatic teletypewriter switching service to a database such as, for example, a computer for transmitting electronic mail, a user accessible library, a computer used for mathematical computations, or other types of databases. More particularly, the present invention relates to a microprocessor operated telecommunications interface for connection to a telecommunications line to provide for transmission of data between a user terminal and a database over a telephone line either using telephone company lines or intermediate carriers. The present invention also relates to a method of interfacing a user terminal with a remote database.
(2) Description of the Prior Art
Many database services exist that are accessable by remote cathode ray tube terminals. The databases may be of various types, such as, for example, electronic mail services, library services, computing services and any other computer assisted services. When a user accesses a database, the user connects his terminal with a database by using a telecommunications modem and enters information into the CRT terminal which identifies the user, the type of terminal and other information required to put the terminal on-line with the database. The user may dial the database either by direct telephone service or by local telephone service and an intermediate carrier, and enter information for hand-shaking with the database including a user code, a baud rate of the user terminal, and various other information used to put the user terminal on line with the database. It is not uncommon for a person using the terminal and the database to be unfamiliar with performing dialing operations.
In order for a user to access a database, the user must purchase or lease a terminal, and if a print-out is desired, a printer. The relatively high cost of acquiring a terminal has discouraged many potential users from using computer database services. However, a large number of terminals for automatic teletypewriter switching services, such as, for example, Western Union TELEX service, or RCA GLOBECOM International Record Carrier Service, are presently in existance. These terminals are usually dedicated to a single use, the transmission and receipt of messages over the service, and further, these dedicated terminals operate at relatively low baud rates, that is baud rates typically below 150 baud, and for TELEX terminals, baud rates of 50 and 110. Communications costs, that is, carrier time charges, and computer time charges would be excessive if dedicated terminals with low operational baud rates were used as remote terminals for communication with a database. Moreover, dedicated teletypewriter terminals, such as a TELEX terminal, having a fewer number of keys, are incapable of communicating with a database in the same manner as a standard CRT terminal.
It would be desirable to provide an interface for a terminal of an automatic switching service that enables a relatively unskilled person to actuate a switch or terminal keys, or a small number of switches or terminal keys, to automatically put the terminal on line with the remote database.
When a teletypewriter terminal is used for electronic mail, that is, sending and receiving of messages, it is desirable for the terminal to be able to compose and edit messages when the terminal is off-line with the database, so that the user does not incur charges for telephone, intermediate carrier, and computer time. Also, with regard to electronic mail, it is desirable for the database to be able to communicate with the user terminal, and, more specifically, the database may receive messages from other terminals that are addressed to a particular user terminal. It would be desirable for the database to be able to either communicate the message to the remote user terminal or signal the remote user terminal that a message is available at the database for the user terminal.
It is known to provide an autodialer for a down-line user terminal, and more specifically, it is known to provide an automatic dialer that performs the operations of network activation, log-on sequencing and hand-shaking with the remote database wherein code, baud rate of the terminal and other protocol information is transmitted to the remote database. However, autodialers known to applicant do not transmit messages to the database, nor do they receive messages from the database.
Conventional autodialers are programmed by the user to access various databases. It would be desirable for a database to be able to reprogram the operations that are automatically performed by the autodialer at the user terminal.